1. Field of the Invention
This invention relates to techniques for determining and positioning the center of a disc precisely over a predetermined location based on the outer diameter of the disc and wherein the outer diameter varies from disc to disc.
2. Description of the Prior Art
When machining parts in high volume, a fixture is typically made which holds a given part in the proper position relative to the cutting tool. The fixture normally has fixed stops or rest elements that press against reference surfaces of the part. The positions of the fixed stops or rest elements determine the relative position of the intended machining operation and the part reference surfaces. For locating a diameter of a disc, a pair of pins is often adequate if the allowable tolerance of the center location is large compared to the variation of the diameter, since the center of the diameter shifts by approximately half the variation in the diameter.
For the case where the allowable tolerance of location of the diameter is not large compared to the diameter variations, simple fixed pins or stops are not adequate to center the disc. This is the case for hard disc memory storage devices, for example.
It is therefore one object of the present invention to provide a precise automatic disc position centering device.
Another object of the invention is to accomplish precise automatic position centering of discs whose absolute outer diameters vary to a degree greater than mechanisms of the prior art can adequately center.
A further object of the present invention is to provide a means of firmly holding each disc in the centered position for clamping and subsequent machining processes.